Steam achievements
Complete the following tasks to unlock the corresponding achievement. To view your achievements and stats in Steam, select "Community", then "My profile", then "View all my games", then the game and view stats.

A Little Help From a Friend: Complete 1 mission in Co-op.
Addict: Win 20 sessions of 'cops & robbers' (ranked match).
Alpha Male: Have the most kills in a Cops & Robbers Ranked Match.
Baby be Safe: Complete 'coming home' on any difficulty.
Battle Hardened: Complete one session in each Multiplayer Mode (Ranked Match).
Blackjack and Hookers!: Accumulate $25,000,000 in your career (Arcade Mode and Multiplayer Ranked Match).
Bring It Down: Complete 'air strike' on any difficulty.
Can It!: Kill 10 enemies with exploding canisters.
Catch!: Push your human shield into an opponent in Story Mode.
Chinese Waltz: Kill 5 enemies without losing your human shield.
D.i.y.: Escape with more than $2,500,000 in a round of either Arcade Mode or Multiplayer Ranked Match.
Dance Off!: Execute 30 enemies while holding them as human shield.
Dead Man Rising: Complete Story Mode on Extreme
Death Sentence: Complete 'Blood, Sweat and Tears' on any difficulty.
Dog Days: Complete Story Mode on any difficulty level.
Doing Good: Successfully reach round 5 in Arcade Mode.
Double Cross: Complete 'the deal' on any difficulty.
Double Happiness: Kill 6 enemies in a row with a shotgun - all of them as one shot kills.
End of the Road: Complete Story Mode in Co-op.
Escape from ...Anywhere: Successfully escape 25 times in Arcade Mode or in any Multiplayer Ranked Match.
Giving a Hand: Finish 30 enemies your co-op partner shot 'down not dead'.
Got Your Back: Revive your Co-op partner 10 times.
Greedy Bastard: Earn at least $5,000,000 in every level in Arcade Mode.
Hand of God: Complete a Story Mode mission without dying once on any difficulty
Harry Houdini: Escape from being held as human shield in any Multiplayer mode (Ranked Match).
Kill or be Killed: Complete 'Resurrection' on any difficulty.
Law Enforcer: Win as the Undercover Cop by killing all criminals yourself (Ranked Match).
Lightning Looter: Reach $8,000,000 in under 6 minutes of actual playtime in arcade mode.
Lost Love: Complete 'a thousand cuts' on any difficulty.
Love of Money: Successfully reach round 10 in Arcade Mode.
Mastermind: Become criminal Mastermind (Highest Rank) in Multiplayer Ranked Match.
Mexican Showoff: Kill 5 enemies while downed before successfully recovering.
Most Wanted: Accumulate $50,000,000 in your career (Arcade Mode and Multiplayer Ranked Match).
No Going Back: Complete 5 missions in Co-op.
No I in TEAM: Earn the highest Criminal Loyalty level in Multiplayer Ranked Match.
Nowhere to Hide: Complete 'laying low' on any difficulty.
Putting on the Ritz: End a round as Criminal Expert in a Fragile Alliance Ranked Match.
Rat Killer: Kill the Undercover Cop as the last surviving criminal and escape (Ranked Match).
Safe Crime: Finish 5 rounds in a row without getting any penalties in arcade mode.
Sichuan Specialist: Escape the restaurant in 'Laying Low' without being downed on any difficulty.
Slow Train to Hell: Complete 'Out of Shanghai' on any difficulty.
Steady Hand: Get 5 headshots in a row using the same clip.
Street War: Complete 'the details' on any difficulty.
The Cleaner: Escape as a traitor with 50% of any level's total loot in either Arcade Mode or Multiplayer Ranked Match.
There's an I in TRAITOR: Become Scum in a Multiplayer Mode (Ranked Match).
Trigger Happy: Kill 5 enemies in 15 seconds with any pistol.
Unfinished Business: Kill a yellow carded criminal whilst Down Not Dead (Arcade Mode and Multiplayer Ranked Match).
Welcome: Successfully escape once in Arcade Mode or in any Multiplayer Ranked Match.
Welcome to Shanghai: Complete 'Welcome to Shanghai' on any difficulty.
You Want Blood?: 1000 kills.

Hitman reference
In the Chapter 2 when you start to fight the police after you pass a bus, Kane tells you to enter the store to your left. Look at the pictures in that store to see Agent 47 from the Hitman series.

Mini Ninjas reference
Play the "Subway" multiplayer level. When you spawn, turn to your left to find five signs. The first one sign features the cast from Mini Ninjas.